Flexible fences are known, to provide an extra measure of protection in addition to typical chain link fences around a swimming pool, which can sometimes to climbed by young children. The flexible fences are too loose for gripping, and therefore prevent a young child from getting unsupervised access to a swimming pool, even if the child climbs over a conventional chain link fence around a swimming pool. Such flexible fences are described in U.S. Pat. No. 5,553,833 of Bohen.
In addition, there are fence plugs with expandable wings of sockets for fence poles, such as disclosed in U.S. Pat. No. 978,505 of Stewart or U.S. Pat. No. 3,159,248 of Biehn. Also quarter turn twist lock posts for fences are described in U.S. Pat. No. 4,007,516 of Coules.
U.S. Pat. No. 4,787,601 of Rybek shows plastic anchor sockets, but they are not expanding.